Assuming an American, Aussie or Kiwi (etc.) presents themselves at the UK border, the landing interview goes perfectly and there's nothing funny about them, about how much time will the officer usually spend checking stuff on the computer?

In other words, how long is it on average from the officer scanning the passport to issuing the entry stamp?

Does it vary between airports (e.g. Heathrow) and seaports (e.g. Calais)?

It's been a long time (maybe 15 years) since the last time I entered the UK with a US passport, but when I did so, the entire landing interview probably took about a minute. I'll leave it to someone with more recent experience to post an actual answer.
– phoogFeb 1 at 12:50

Is the question about the entire landing interview or scanning the passport on the computer?
– user 56513Feb 1 at 15:30

I'm not sure that there's any data on this besides anecdotal experience. I entered at Paris (Eurostar) with a US passport last year. He scanned the passport, asked me three times if I was going to work. I said no three times. He tapped some keys. Stamped my passport. Maybe 30-45 seconds all told.
– Zach LiptonFeb 1 at 19:28

Starting later this year US passport holders (among many others) will be able to use the smart gates. In this case you won't have a landing interview at all.
– Michael HamptonFeb 1 at 23:28